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Commissioning An Orthovoltage Unit Used for Radiobiology Research

R Azimi

R Azimi*, P Alaei, S Hui, Univ Minnesota, Minneapolis, MN

SU-E-T-272 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: Torthovoltage X-ray units are used to irradiate cell cultures or small animals in research. Beam characteristics of these units are often not well understood and only nominal dose specified is used by researchers in their studies. This work describes commissioning of an orthovoltage unit similar to that of a linear accelerator.

Methods: The X-Rad 320 Orthovoltage unit is a self-contained x-ray system which can be operated within a wide range of kVp and mAs settings. This work characterizes the beam produced by this system. Various beam data, including depth dose, cross profiles, collimator and total scatter factors, have been measured.
Collimator and total scatter measurements were done with cylindrical farmer chambers (0.6 cc and 0.057 cc volumes) for field sizes ranging from 2x2 to 20x20 cm². Sc measurements were done in air at 50 cm SCD and Sc,p measurements were done in 2 cm depth of phantom at 50 cm SSD.
The depth dose curves were generated for three different field sizes for depths up to 15 cm. A parallel plate chamber was used for surface and near surface dose measurements while the cylindrical chamber was used for other depths.

Results: Measurements of Sc and Sc,p indicate minimal variation of these factors with field size, except for very small fields. The results of depth dose measurements produce results comparable with published data for similar beams and indicate a very small dose buildup at shallow depths.

Conclusions: Proper characterization of an x-ray beam and accurate dosimetry is of importance in radiobiology investigations which may lead to advent of new therapies for humans. This work investigates the beam characteristics of an orthovoltage unit to ensure accurate irradiation of samples. The data collected here could further be used for simulation of dose distribution within irradiated volume.

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